Electronic speed controlling apparatus



April 22, 1958 J. R. BOYKIN ELECTRONIC SPEED CONTROLLING APPARATUS 4Sheets-Sheet 1 Original Filed Nov. 4, 1950 uman k4 W INVENTOR Johh R.Boykin.

A ril 22, 1958 J. R. BOYKIN 2,

ELECTRONIC SPEED CONTROLLING APPARATUS Original Filed Nov. 4, 1950 4Sheets-Sheet 2 Exhaust Idle M 17/ Vary TbroIt/e Fl I 3 I INVENTOR G-John R. Boykin.

REM. .9 /.0

ATTORNEY April 22, 1958 .1. R. BOYKIN ELECTRONIC SPEED CONTROLLINGAPPARATUS 4 Sheets-Sheet 3 Original Filed Nov. 4, 1950 INVENTOR John R.Boykin.

April 22, 1958 J. R. BOYKIN 2,831,632

ELECTRONIC SPEED CONTROLLING APPARATUS Original Filed Ndv. 4, 1950 4Sheets-Sheet 4 John R. Boykin.

ATTORNEY United States Patent 7 Claims. (01. 23561) My inventionfrelates to the control of a jet engine having a fuel valve andavariable exhaust nozzle and,

moreparticularly, of such an engine provided with means operative inresponse to the speed and temperature of the engine to controlautomatically the operation of the fuel valve and the exhaust nozzle foradjusting the thrust of the engine. In certain of" the more generalaspects, my invention is applicable to an engine of any This is adivision of Serial No. 194,153, filed Novemher-"4, 1950, and assigned tothe assignee of'this invention.

My application is relatedto" an application of Cyrus F. Wood, filedOctober 13, 1949, Serial No. 121,171, now Patent No. 2,734,340, andassigned to the Westinghouse Electric Corporation.

A jet engine of the type primarily under consideration involves threevariables, namely, engine speed, nozzle area and engine temperature, anytwo of which may be varied, with the third fixed in relation thereto, tovary the thrust. In its broader aspects, the present inventioncontemplates movement of a manual throttle lever to increase the thrustby increase in fuel input for operation to the extent of the maximumtemperature the engine will stand. Preferably, however, movement of thethrottle lever for increase in thrust involves speed and temperaturecontrolling effects or signals for controlling the fuel input and theexhaust nozzle discharge area for development of propulsion thrust overthe thrust range. From idling to about 75 or 80% of full engine speed,the speed signal is used to control increase in fuel input for increasein' engine speed and thrust; and, while the speed signal also tends tooperate the exhaust nozzle to increase the nozzle discharge. area, assuch nozzle is already in maximum area-defining position over thisengine speed range, it has no eifect thereon, with the result thatincrease in power, represented by increase in fuel input, is effectivefor rapid engine acceleration. With the engine operating at 75 or 80% offull speed and the exhaust nozzle in maximum area position, the thrustmay be increased over a relatively much larger percentage of the thrustrange by a small percentage of engine speed change coupled withrestriction in nozzle area. While each of the speed and temperature.signals exert eifects on the exhaust nozzle and on the fuel input, theydo so differently in actual practice--the speed signal tending toincrease the fuel input and the exhaust nozzle discharge area whenactuated from the idling to the full engine speedpositions and thetemperature signal tending to increase the fuel input and to reduce theexhaust discharge area to'increase the thrust when actuated over thisrange.

Preferably, control of the engine is effected electrically, the enginedriving an alternator operating through a frequency meter and amplifiersto control the exhaust nozzle and the fuel valve, and a voltageresponsive to temperature is amplified and serves also to control thenozzle and the fuel valve. Such network includes settings 2,831,632,Patented Apr. 22, 1958 adjustable manually to change the fuel input orthe latter and the nozzle area to vary the thrust.

More particularly, the invention involves an electronic power regulatorcontrolling the exhaust nozzle and the fuel valve. The regulatorincludes an alternating-current generator driven by the engine,direct-current sources, and speed and temperat'ure settings, arranged inthe cockpit and operable by means of a throttle lever. Speed andtemperature direct current voltages are derived from the alternatoroutput and cooperate with setting direct current voltages from the speedand temperature settings to provide, in the event of deviation of thederived and setting voltages from balanced relation, direct-currentspeed and temperature signals, 'thepolarity of each of which dependsupon the direction of deviation. A fre-,

quency determining network is provided to measure the frequency of thealternator, and, therefore the speed of engine, at all times duringoperation. Temperature is measured by a thermocouple properly disposedin the engine.

There are provided two modulators, one being the exhaust nozzlemodulator and. having its output supplied to an electronic amplifyingnetwork to control a servo for operating the exhaust nozzle and theother being the fuel input modulator and having its output supplied toan electronic network controlling a servo-motor for operation of thefuelv valve to vary the fuel input. Each of the modulators is suppliedwith direct-current inputs including said speed and temperature signalsand with alternating-current input supplied from the alternator, andoperates to provide an alternating-current output, the amplitude ofWhose wave is proportional to the directcurrent input and which output,at alternator frequency, isimpressed on the exhaust nozzle and fuelvalve electronic control networks. As long as the resultant signal inputis zero for each modulator, the alternating-current output of each ofits respective electronic network is zero; however, if the signal has anegative or positive polarity, the modulator has analternating-currentoutput at alternator frequency with the output Wavefor a negative signal input 180 degrees out of phase relative to'theoutput when thesignal is positive. If the speed signal is negative, thealternating-current outputs of the modu-" lators tend to open theexhaust nozzle and'to open wider the fuel valve; and, if the speedsignal is positive, the

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contrary operation takes place, the tendency being for the exhaustnozzle to close and for the fuel valve to move in a closing direction.If the temperature signal goes negative, the fuel valve modulatorresponds in' the same way as for anegatives'peed signal, that is,it'causes the fuelinput to increase; however, because of thedifferentway in which the temperature signal is applied'to the exhaustnozzle 1nodulator, the alternating-current outputof'the latter will bedegrees out of phase compared to its output for a negative speed signal,in consequence of which the exhaust nozzle discharge area will berestricted. If the temperature signal goes positive, the contraryoperation takes place. I

When the. enginereaches a certain temperature above which safety maybein question, temperature control overrides all other controls. With theengine above this safe temperature the control operates to cut down fuelsupply regardless of the settings of any of the control components. Inthe control of an engine equivalent to the J-34- engine (Navynomenclature). the maximum safe temperature is 1250 F. Above thistemperature thecon- I trol operates to cut down fuel supply. If thetemperature reaches 1400 F., fuel supply is abruptly cut to minimumflow.

In addition to the signal inputs to the exhaust nozzle and fuel valvemodulators, additional inputs are'supplied thereto. A stabilizingfeedback input controlled by movement of the exhaust nozzle is suppliedto the exhaust nozzle modulator, and the feedback connection is arrangedso that a smaller speed or temperature signal is required for moving theexhaust nozzle in a closing direction than in an opening direction.Aside from speed and temperature inputs supplied to the fuel valvemodulator, the latter has a stabilizing feedback input and atemperature-limiting input controlled by movement of the fuel valve, thepurpose of the temperature limit being to anticipate temperature, thatis, to prevent overtravel of the fuel valve in an opening direction andconsequent oversupply of fuel and overheating of the engine.

The frequency determining circuit including the voltaeg doublers isanalogous to a circuit shown in Fig. 4 of British specification 619,139.This latter circuit includes a frequency doubler comprising a capacitorC1, the output of which varies with frequency and a second frequencydoubler including capacitor C4, the output of which varies with theamplitude of the impressed voltage. In the British system the outputvoltages of the frequency doublers are balanced against each other and acorrecting voltage is derived through conductor 1. In operation, I havefound that a jet engine including a circuit of this type, at timesvibrates violently.

Accordingly, one specific object of my invention is to provide a controlfor a jet engine which control shall not produce violent vibrations inthe operation of the jet engine.

The aspect of my invention involving this object arises from myrealization that the cause of the violent vibration may be ascribed tothe British frequency determining network. The components of the Britishsystem are so related that if a sudden change takes place in an externalvoltage (such as may be caused by load change on the alternator due tothe firing of the fuel valve control thyratrons to change the fuel flowto the engine and hence alternator speed), the output conductor 1 wouldcarry a transient pulse which would produce a transient dlsturbance inthe system to which the frequency determining device is applied. Thistransient pulse so derived at the output conductor would cause thevoltage output of the alternator to change suddenly, which would, inturn, introduce a sudden counter-change into the correcting circuitwhich would, in turn, cause a corresponding sudden counter-change in thealternator. This periodic operation would give to the engine and thecraft on which it was mounted an objectionable and vigorous vibration.

An ancillary object of the invention is accordingly to provide animproved frequency responsive network which is less subject toobjectionable transients than those of the prior art.

An additional ancillary object of the invention is to provide animproved frequency responsive device which will satisfactorily functionunder the conditions of jet engine control operation.

A further ancillary object is to provide a frequency responsive networkwhich will give a reliable and accurate indication of jet engineoperational speeds, with particular emphasis on the maximumsafe-operational speed.

A still further ancillary object is to provide a frequency responsiveapparatus which can be made an operationally integral part of anelectronic control apparatus for a jet engine.

My invention is based on the realization that the transient difiicultysprings from the fact that the transients are caused by the relationshipbetween the impedances in the circuit of the British voltage doublers.The resistor R1 is of too great value compared to the resistor R3(600,000 ohms as compared to 4,700 ohms) and the relationship betweenthe capacitor shunting the resistor R3 and the capacitor C1 is notproper. Because of this relationship, a sudden change resulting in apulse supplied through the capacitor C1 is in no respect counterbalancedby an opposite polarity signal applied through the resistor R1 which isof very high magnitude.

In accordance with my invention, a frequency determining network isprovided in which the resistors and the capacitors are so related thatany transients produced by a sudden change in the voltage impressed fromconductor A are suppressed.

In the operation of a jet engine, separate direct-current voltagesrespectively for speed and temperature are manually preset by theaircraft pilot. These voltages must be compared with direct-currentsignal voltages which respectively measure the speed up and temperatureoperational conditions of the engine, and are derived from the enginecomponents which are controlled and detection apparatus suitablydisposed to measure the actual speed and temperature of the engine. Oneof these latter derived signals, the direct-current speed signal, isdependent on the output of an alternator operated by the engine, and ismeasured by a frequency determining network which gives an outputdirect-current speed signal corresponding to the frequency of the outputvoltage from said alternator. Another of the latter derived signalvoltages is measured by thermocouples suitably disposed to determine theoperational temperature of the jet engine. It is desirable that anychange in the values of the preset voltages or the derived voltages willproduce immediate correcting action in the operation of the engine.

It is, accordingly, an object of my invention to provide a servo systemwhich is responsive to a plurality of command signals and which shalloperate promptly and precisely to produce correcting action.

My invention arises from the realization that polarity changes are morereadily identifiable by electrical pickup components than magnitudechanges. In accordance with my invention, the preset voltages and thederived signal voltages are balanced against each other so as to supplya zero output voltage to the pick-up device during steady stateoperation of the engine. So long as the preset voltages are fixed, andthe engine speed and temperature remains constant, this output remainsat a zero magnitude and the operation of the engine does not vary. If,however, the preset voltages are changed by the aircraft pilot or theengine speed or temperature changes slightly, a positive or negativeresultant net voltage is impressed on the pick-up devices.

The novel features that I consider characteristic of my invention areset forth with particularity in the appended claims. The inventionitself, however, both as to its organization and its method ofoperation, together with additional objects and advantages thereof, willbest be understod from the following description of specific embodimentswhen read in connection with the accompanying drawing, in which:

Figure l is a diagrammatic view of a jet engine, the operation of whichmay be controlled by a regulator in accordance with my invention;

Fig. 2 is a graph showing exhaust nozzle discharge area, thrust,temperature, and speed variations as a function of throttle position forthe jet engine shown in Fig. 1;

Fig. 3 is a graph showing the relation of thrust to engine speed at theupper end of the speed range for the jet engine;

Fig. 4 is a schematic diagram of a frequency determining network inaccordance with my invention;

Fig. 5 shows a block diagram of the electronic regulator illustrated inFig. 1;

Fig. 6 is a circuit diagram of a frequency meter embodying amodification of one aspect of my invention;

Fig. 7 is a graph illustrating the operation of the frequency meternetwork included in Fig. 4 as shown in Fig. 6.

In Fig. 1, there is shown a jet engine 7 having an adjustable exhaust orpropulsion jet nozzle 8 and fuel valve 9. In addition to the fuel valveand the jet nozzle, the engine comprises a turbine 10, a compressor 11,and a combustor 12, the compressor delivering air to the come bustor forgeneration of motive fluid to drive "the turline, the turbine drivingthe compressor and the exhaust from the turbine undergoing furtherexpansion in the nozzle to provide the propulsion jet. The exhaustnozzle has a component or components 13 moved by the servomotor 14 tovary the exhaust nozzle discharge area and the fuel valve 9 iscontrolled by the servo-motor 16 to vary the fuel input.

Jet thrust is varied by manual adjustment of a setting of a powerregulator controlling the fuel input, or the latter and the exhaustnozzle area, in response to engine speed and temperature. As shown inFig. 1, the regulator has speed and temperature settings, M17 and at 18,operated by a throttle lever 19. Upon movement of the lever 19 forsetting adjustment, the balanced relation of the regulator is disturbedand the latter is thereby rendered effective to adjust the fuel valve,or the latter and the exhaust nozzle, for engine operation to restorethe balanced relation and thereby to vary the jet thrust in accordancewith lever movement.

Referring to Figs. 2 and 3, with the engine idling, as the throttlelever is moved in the direction of increased speed and thrust, thechanging temperature setting has no effect on the automatic controlmecahnism until the speed reaches about 75 or 80 percent of full speed,the control during this acceleration period being mainly in response tospeed with the exhaust nozzle fully open.

At about this fractional speed, the temperature control comes into playmainly for the purpose of closing the exhaust nozzle so that in goingfrom said 75 to 80 percent speed point to full speed, the ratio ofthrust change to speed change rapidly increases with the result that, atfull speed, and as may be seen from Figs. 2 and 3 and particularly Fig.3, only a very smallpercentage of speed change is required for a largepercentage of thrust change. Therefore, while the operator moves thethrottle lever to vary the thrust, this result is accomplished byvarying the nozzle and the fuel input through the intermediary of theautomatic control arrangement responsive to speed and temperature, thearrangement assuring of correlated operation of the exhaust nozzle andfuel valve in response to speed and temperature with the maximumdevelopment of thrust without going to temperatures too high forallowable turbine toleration.

The regulator includes a speed network (see Fig. 4), which, inconjunction with the manually set speed and temperature settings,provide direct-current signals to the exhaust nozzle modulator, and tothe fuel valve modulator, and each of the modulators has an alternatingcurrent output, whose frequency is the sameas that of the alternator,and whose amplitude and phase, respectively, depend upon the magnitudeand polarity of the directcurrent speed and temperature signals;

Speed-sensitive network The speed-sensitive network 28 comprises (Fig.4) a reference component 60, a frequency-responsive compo nent 61, andthe manual setting at 17. In operation, the currents provided by thereference component 60, by the frequency-responsive component 61, and bythe manually-operable setting 17 are in balanced relation, with theresult that, if the setting voltage is changed, current is supplied toor drawnfroin the modulator;

The reference component 60 comprises an impedance and rectifier networkof the doubler type and it includes a condenser C117 connected to phaseA through relatively large line resistors which decrease the effect ofharmonics on the system. The frequency-responsive component 61 includesparallel condensers C120 and C139 connected to phase A.. The capacity ofthe condenser C117 is relatively large compared to that of theparallel-connected condensers C120 and C130 of the frequency counter 61,with the result that the voltage of the former changes quite rapidlywith the change in frequency, in consequence of which, for the operatingrange, a substantially constant reference current and voltage may beprovided over a range of frequency variation. On the other hand, becauseof the relatively much lower capacity of the condensers C120 and C139 ofthe frequency-responsive network, the frequency-responsive voltage andcurrent vary substantially in linear relation to speed, with the resultthat a change in setting 17 voltage produces a speed signal which bringsabout change in engine operation until the saidsigual is restored tozero under the latter condition of operation, the reference 60, thefrequency-responsive component 61, and the setting 17 currents arebalanced, and the resultantspeed signal onthe line 31 is equal to zero.In the subsequent discussion of the graphical representation of thecurrents shown in Fig. 7 for the reference branch and the frequencyresponsive branch 61 this circuit is further explained.

In addition to the condenser C117, the reference component 60 includesbranches 65 and 66 connected to condenser C117. The branch 65 includes arectifier Cit-1119, conductive from the condenser C117 through theparallel branches 68 and 69 to ground, the branch 63 including acondenser C118 and the branch 69 including resistances R135 and R136.The latter speedsetting resistance R136 is adjustable to vary thepotential applied to the condenser C118 and, therefore, the voltage dropacross the condenser C117 and its charge. The resistance R136 ispreferably adjusted for full speed values of the reference component 60current and voltage.

The branch 66 is connected through the rectifier CR-llS, to beconductive toward the condenser C117 from parallel branches 70, 71 and72. The branch is connected, through resistance R138 and parallelconnections 74 and 75 to ground: the connection 74 including thecondenser C121 and the connection 75 including the resistances R139 andR140. The branch 71 includes a resistance R137 connected to thereference line 76. The branch 72 is connected through the condenser C119to ground.

When phase A is positive relative to phase B, conductionfrom A to Boccurs through the condenser C117, the rectifier CR109, andthercondenser C118. If B is positive, then conduction occurs through thecondenser C119, rectifier CR- and the condenser C117. Since thecondensers C118 and C119 are in effect connected in series between 55aand 56a, with the ground, or phase B, serving as a midpoint connectionbetween the condensers, and since such condensers are charged onsuccessive half cycles, the voltage from 55a to 5641 is double the inputvoltage to C117. I

Thecycle counter or frequency'sensitive component 61 includesparallel-connected condensers C .and C130, joining the phase A line 62with the branches 78 and79. The branch 78 includes a rectifier CR-110conductive from ground, or phase B, through the parallelconnectedresistance R155 and condenser C122. The branch 79' includes a rectifierCR-111 conductive to terminal 80 to which the reference line 76 isconnected; On positive half cycles, conduction occurs through thecondenser C120 and C and the rectifier CR-111 to the terminal 80. Onnegative half cycles, conduction occurs from ground, or phase B, throughthe parallelconnected resistor R and condenser C122, the rectificrCR-110, and the parallel conne'cted condensers C126 and C133 to line Dueto the parallel-connected condensers C120 and C136, there is providedimpedance varying inversely to frequency, in consequence of which directcurrent in the connection 81 is proportional to frequency.

The terminal 80 is connected to ground through the condenser C123, andthrough the connection 82 to the speed setting line from the manualspeed setting.

Representing the reference direct current in the line 76 (Fig. 4) as x,the frequency current of line 81 as y and the setting current providedby the speed setting line 84 (Fig. as z, a steady state or balancedcondition exists when the terminals 80 and 83 are at equal potentials.This exists when 1 is equal to x minus 2. If 2 is decreased withincrease in speed-setting, current is drawn through the line 31 from themodulators, that is, a negative speed signal is furnished to themodulators. On the other hand, if z is increased, a positive speedsignal is applied. In other words, as long as x minus 1 is made largerthan y, a negative speed signal is applied, and, when the difference issmaller than y, a positive speed signal is applied.

To suppress transients and the resultant engine vibration inducedthereby, respecting the frequency network components, it was found that,roughly, the capacitor C119 should be of the same magnitude as thecapacitor C117, and the capacitor C118 should be 50% greater than thecapacitor C117: the resistor R137 should be substantially equal to thesum of resistors R135 and R136. The frequency responsive network 61 hasso short a time constant as not to be materially affected by thetransients. In a preferred system in accordance with the invention, theresistor R137 has a magnitude of 50,000 ohms: the resistors R135 andR136 combined have a resistor slightly greater than 50,000 ohms (thevoltage divider R136 has a maximum resistance of 10,000 ohms) thecapacitor C119 has a capacitance of .5 microfarad and capacitor C118 hasa capacity of .75 microfarad. In this system the capacitor C117 has acapacity of .5 microfarad. The magnitudes given here were determined bycareful selection after it was realized that the objectionablevibrations which arise if a system such as is disclosed in the BritishPatent 619,319 is used, could be suppressed by such selection.

System as a whole In Fig. 5 is shown a simplified block diagram showingsome of the major control components of the control system in blockdiagram. The frequency meter 28 is shown as a block diagram having itsoutput fed through line 31 to the exhaust nozzle modulator 33 which isalso shown as a block. The D. C. speed signal output from the frequencymeter which passes along line 31 is fed to fuel valve modulator 34 alongspeed signal cross fed con nections 31a and 31b. The thermocoupleamplifier 29, shown as a block, amplifies the very low D. C. voltageoutput of the thermocouple 26 to give a D. C. temperature signal outputwhich is also fed to modulator 34. The temperature signal crossfedconnection 32a from the thermocouple amplifier 29 to the exhaust nozzlemodulator 33 is shown. ship between modulator 33, exhaust nozzleamplifier 36, and phase sensing power amplifier 37 to cntrol the exhaustnozzle servo 14 is shown. The relatively direct line relationshipbetween modulator 34, fuel valve of modulator44 and phase sensing poweramplifier 45 to control the fuel valve motor 16 is also shown. Theexhaust nozzle feedback network 116 is shown coupled through line 118back through a variable resistance circuit to be fed into the input ofmodulator 33. The fuel valve feedback circuit comprising potentiometer121 connected through lead 123 back to the input of modulator 34 isshown. The pilots manual lever 19 which changes the resistance ofpotentiometers 18a and 17a to introduce speed and temperature changevoltage components is shown. The various limiting circuits and variableresistance networks are shown in their proper circuit relationship.

Modified frequency meter In Fig. 6 is shown a modified circuit for useas the frequency meter network 28. In lieu of the rectifiers CR-109 andCR-115, as shown in Fig. 4, two vacuum tube diode rectifiers 210 and 212may be employed; and, instead of the selenium rectifier elements CR-110and CR-111 shown in Fig. 4, there may be substituted two vacuum tubediodes 214 and 216. The remaining circuit The relatively direct linerelationof the frequency network 28 remains basically the same as thatshown in Fig. 4. Condenser C154 which has been chosen to compensate forthe temperature effects on the valves of the various other componentshas been substituted for previous condensers C and C130. This condenserhas a negative capacity temperature coefiicient. The substitution of thevacuum tube diode rectifiers under certain conditions of operation maybe more suitable in view of the effect of high temperatures upon thecharacteristics of certaintypes of rectifier elements, such as seleniumrectifier elements.

Operation of frequency meter In Fig. 7 are shown the current curves,plotted with frequency F as the abscissa and the current divided by theimpressed signal voltage,

as the ordinate, for the two branch networks 60 and 61 of the frequencymeter 28. The curve 200 of the current output of the frequencyresponsive rectifier branch 61 is substantially linear over thefrequency range of operation of the engine, since the current derivedfrom branch 61 varies directly with frequency. The current of branch 60varies directly with frequency over a short range at low frequencies andbeyond this change is substantially constant. This current isrepresented by curve 201. Accordingly, the current of branch 61 may beexpressed as a function of frequency by the equation and, beyond the lowfrequency range where the current of branch 60 varies, this latter maybe expressed by the equation At a frequency F the two currents areequal. At this frequency kF =K That is, F is a constant independent ofthe voltage E The summation current represented by curve 202 is balancedagainst the current received over line 84 (in Fig. 5) from the manualspeed setting 17. When the latter currents are balanced, the speedsignal sent to the modulators over line 31 is zero to bring about nochange in the engine operation.

The frequency F corresponds to the condition of opera tion at which thecurrents through branches 60 and 61 are balanced against each other.This frequency arises in actual operation only if the current frompotentiometer 17 is zero, that is, at the highest engine speed (militaryspeed). At other speeds of the engine the actual frequency is less thanF At these latter speeds the current from the potentiometer 17 isbalanced against the net current from the frequency meter; that is thedifferent current between the current of curve 200 and the current ofcurve 201 is balanced against the current from potentiometer 17 It isessential that the frequency F be maintained constant independent oftemperature variations. It is for this reason that I have provided thetemperature compensating condenser C150. This condenser is so selectedas to compensate for the variations with tempera ture of all of thecomponents of the meter.

Operation area in response to magnitude and polarity of speed andtemperature signals applied to the modulator 33, and 1t controls thefuel valve in response to the magnitude and polarity of the algebraicsum of speed and temperature signals applied to the moduiator 34. Eachmodulator 33 or 34 operates to provide an alternating-current outputwave 244 whose amplitude depends upon the magnitude of a speed andtemperature direct-current signal input wave 242, with the wave 244 fora negative signal out of phase by 180 degrees with respect to that for apositive signal. The alternating current output of each modulator isamplified and furnished to a phase-sensitive amplifier supplying thecorresponding servo, t to arrangement being such that negative speedsignals cause in-. crease in nozzle area and in fuel input and viceversa and negative temperature signals cause decrease in nozzle area andincrease in fuel input and vice versa.

The direct current speed and temperature signal inputs are provided bymeans responsive to engine speed and temperature and bymanually-controlled adjustments. The speed signal, by means of themanually-movablesetting 17, is made to give a negative speed signaleffective on the modulator 33 to cause opening of the exhaust nozzle andeffective on the modulator 34 to increase the fuel input.

Temperature-responsive means 29 operates to provide an output, normallynegative, and which, with positive and negative limits, provides asteady-state temperature signal which is made negative by throttleadjustment for increase in speed. The steady-state temperature signal soprovided and modified is applied to both modulators 33 and 34. It isapplied to the exhaust nozzle modulator 33 in such a manner that thealternating current wave caused thereby is 180 degrees out of phase withrespect to the wave caused by a speed signal of like polarity, with theresult that a negative temperature signal tends to close the exhaustnozzle and open the fuel valve.

The means by which a speed signal is applied to the fuel valve modulator34 has means limiting the extent of negative polarity of such signal tolimit the increase in the fuel input thereby.

In addition "to the speed and temperature signal inputs for themodulator 33, the latter is also supplied with neutralizing or follow-upinputs depending upon exhaust nozzle position. Therefore, if a negativecombinationspeed and temperature signal is applied to the modulator tobring about opening of theexhaust nozzle, such opening results in theapplication of an increase in positive feedback signal to the modulatorto neutralize the negative combination signal, whereupon movement of theexhaust nozzle ceases. This follow-up or feedback connection includesmeans whereby a smaller combination signal is required for closing theexhaust nozzle than for opening it, so the nozzle may be closedmorerapidly thanit is opened. I

In addition to the limited speed signal and the steadystate temperaturesignal applied to the fuel valve modulator 34, there are temperaturelimit and fuel valve feedback or follow-up signals. Assuming a negativeinput signal to be applied to the fuel valve modulator 34, then, as thefuel valve opens, an increase in positive signal is fed back toneutralize the negative input signal to stop further opening of the fuelvalve.

A temperature limit signal is applied to the modulator to avoidexcessive fuel input, particularly when the engine is accelerating. Tothis end, there is provided the temperature limit line 128, includingfirst and second sections 127 and 129 connected by a rectifier CR-103awhich is conductive from the first section 127 to the second section129. The first section is connected to the outlet terminal of thethermocouple amplifier 29 through a resistance R168 and the secondsection 129 is connected through a resistance R118 to the modulator 34.Normally, the potential of the first section 127 is negative, and thesecond section 129 is kept from going negative by a rectifier CR-103bwhich is conductve from ground thereto. The resistance R118 connectingthe sec- 10 ond section 129 to the modulator-34 assures, not only of asignal applied to the latter which is normally negative relative to thesecond section 129 at ground potential, but it serves to limit theextent to which the terminal 53a of the modulator 34 may go negative. Aslong as no direct current is fed back from the fuel valve to the firstsection 127, there is no effect on the steady-state operation; however,just as soon as the feedback is sufiicient to make the first section 127positive relative to ground, the negative signal causing opening of thefuel valve and consequent rise in engine temperature are limited. I

Since the setting voltages are obtained from rectifiers supplied fromthe alternator, such voltages are lowered for increase in speed andtemperature, with the result that the closest regulation is secured attop speed and temperature.

While I have shown my invention in several forms, it will be obvious tothose skilled in the art that it is not so limited; but is susceptibleof various other changes and modifications without departing from thespirit thereof, and I desire, therefore that only such limitations shallbe placed thereupon as are specifically set forth in the appendedclaims.

I claim as my invention:

1. In an electrical network for controlling the speed of a moving body,said network being operative with a source of control voltage which isproportional to said speed, the combination of a source of speed settingvolt age, a first branch circuit including a first capacitor, a secondbranch circuit including a second capacitor, said first capacitor havinga larger capacitance than the capacitance of the second capacitor, withsaid first branch circuit connected to said source of control voltageand being operative to provide an output reference voltage, with saidsecond branch circuit connected to said source of control voltage andbeing operative to provide an output frequency-responsive voltage, and acircuit junction connected to said first branch circuit, said secondbranch circuit and said source of speed setting voltage for combiningsaid output reference voltage, said output frequency-responsive voltageand said speed setting voltage to produce a resultant voltage .at saidjunction forcontrolling the speed of said body.

2. In speed sensitive apparatus which is operable with a source ofcontrol voltage, said control voltage being proportional to the speed ofa moving body, the com bination of a source of speed-setting voltage, afirst circuit means including a first capacitor having a pair of plates,with one of said plates connected to said source of [control voltage,said first circuit means also including aifirst pair of unidirectionalconductive devices which are connected to be respectively conductivetoward and away from the other plate of said first capacitor, a secondcircuit means including a second capacitor having a pair of plates, withone of the plates of the second capacitor being connected to said sourceof control voltage, said second circuit means including a second pair ofunidirectional devices which are connected to be respectively conductivetoward and away from the other plate of said second capacitor, saidfirst capacitor having a capacitance which is larger than thecapacitance of the second capacitor, said first circuit means furtherincluding a first parallel circuit connected in series with one of saidfirst pair of devices and a second parallel circuit connected in serieswith the other of said first pair of devices, with each of said firstand second parallel circuits including a parallel-connected resistor andcapacitor and a circuit junction connected to said source ofspeed-setting voltage, said first circuit means and said second circuitmeans to produce a resultant voltage at said junction for con trollingthe speed of said body.

3. The apparatus of claim 2 with the capacitor of said first parallelcircuit having a capacitance which is sub 11 stantially equal to thecapacitance of said first capacitor.

4. The apparatus of claim 3 with the capacitor of the second parallelcircuit having a capacitance which is at least one and one-half timesgreater than the capacitance of said first capacitor.

5. The apparatus of claim 2 with the resistor of the first parallelcircuit having a resistance Which is substantially equal to theresistance of the resistor of the second parallel circuit.

6. 'In an electrical apparatus operable with an electrodynamic generatorhaving a pair of terminals and being capable of supplying alternatingvoltages, the combination of a first capacitor having a pair of plateswith one of its plates connected to one terminal of said generator, apair of rectifiers having a pair of electrodes With one electrode ofeach of said rectifiers connected to the other plate of said firstcapacitor in such a manner as to conduct current respectively to andaway from said first capacitor, a second capacitor connected between theremaining electrode of one of said rectifiers and the other terminal ofsaid generator, a third capacitor connected between the remainingelectrode of the other of said rectifiers and said other terminal ofsaid generator, a fourth capacitor of substantially smaller magnitudethan said first capacitor, said fourth capacitor having a pair of platesand having one plate connected to said one terminal of said generator,21 second pair of rectifiers having a pair of electrodes, with oneelectrode of each of said second pair of rectifiers connected to theother plate of said fourth capacitor in such manner as to conductcurrent respectively to and away from said fourth capacitor, a firstresistor having one terminal connected to the second capacitor and theelectrode of the first pair of rectifiers to which said second capacitoris connected, said first resistor having another terminal connected tothe remaining electrode of one of said second pair of rectifiers, asecond resistor having one terminal connected to said third capacitorand to the electrode of said first pair of rectifiers to which saidthird capacitor is cnnected, said second resistor having anotherterminal connected to said other terminal of said generator, said firstand second resistors being of substantially equal magnitude and saidsecond and first capacitor being of substantially equal magnitude, asource of speed-setting voltage, and means interconnecting the junctionof the other terminal of said first resistor and said remainingelectrode of the said one of the second pair of rectifiers with saidsource of speed setting voltage to produce a resultant voltage forcontrolling the speed of said generator.

7. In an electrical network operable with an electrodynamic generatorcapable of supplying an alternating voltage, said generator having apair of terminals, the combination of a first capacitor connected to oneterminal of said generator, a pair of rectifiers, each of saidrectifiers having a pair of electrodes and one electrode of eachrectifier connected to said first capacitor in such manner as to conductcurrent to and away from said first capacitor, a second capacitorconnected between the remaining electrode of one of said rectifiers andthe other terminal of said generator, a third capacitor connectedbetween the remaining electrode of the other of said rectifiers and saidother terminal of said generator, a fourth capacitor of smallermagnitude than said first capacitor connected to said one terminal ofsaid generator, a second pair of rectifiers having respectively a pairof electrodes and one electrode'of each rectifier connected to saidfourth capacitor in such manner as to conduct current respectively toand away from said fourth capacitor, a first resistor having oneterminal connected to said second capacitor and said remaining electrodeof said one rectifier of the first pair of rectifiers, said firstresistor having another terminal connected to the remaining electrode ofone of said second pair of rectifiers, a second resistor having aterminal connected to said third capacitor and to said remainingelectrode of said other of the first pair of rectifiers, said secondresistor having another terminal connected to said other terminal ofsaid generator, said first and second resistors having substantiallyequal resistances, said third capacitor having a capacitancesubstantially one and one-half times greater than the capacitance ofsaid first capacitor and the capacitance of said second capacitor, suchthat transients arising from sudden changes in the amplitude of thevoltage of said generator are substantially suppressed, a source ofspeed setting voltage, and means interconnecting the junction of theother terminal of said first resistor and said remaining electrode ofthe said one of the second pair of rectifiers with said source of speedsetting voltage to produce a resultant voltage for controlling the speedof said generator.

References Cited in the file of this patent OTHER REFERENCES ElectronicInstruments (Greenwood), 1948, pages 340-.

